New Magnetotelluric Study of the East Anatolian Fault Zone and Malatya Fault in Türkiye

The East Anatolian Fault Zone and Malatya Fault are located in eastern Türkiye and are among the most seismically hazardous faults in the region. After the 2023 M7.8  Kahramanmaraş/Pazarcik earthquake, the seismic risk in this area has further increased. We conducted magnetotelluric surveys in this region and obtained a profile containing 33 magnetotelluric measurement points. The apparent resistivity in this region is generally low, with an average apparent resistivity of several tens of Ωm, and shows little variation with depth. We used phase tensor technology to obtain two-dimensional deviation and phase tensor rotation invariants along the profile, and the conclusion is that the structure shows strong two-dimensionality in most areas along the profile, with only local areas showing strong three-dimensionality. We used the ModEM ADORA (Liu et al., 2024) magnetotelluric three-dimensional inversion system with arbitrary data rotation angles to invert the data, where the data maintained the acquisition direction and the grid was rotated 60°. This method can reduce the number of grid divisions, which not only saves computational time but also reduces the underdetermination of inversion. After calculations using different parameters and different grid divisions, we selected the result with better fitting degree and ultimately obtained the electrical structure profile across the Malatya Fault and East Anatolian Fault. The electrical structure reveals that the East Anatolian Fault is underlain by a boundary between high and low resistivity bodies. The formation of the Malatya Fault zone may be related to low-resistivity structures from deep sources that may be associated with fluids or high-temperature materials.